[efoods]Update your twitter in class and you might get a glare from your professor. Tweet at a G20 Summit protest and you could get arrested.

That’s exactly what happened to Elliot Madison—a 41-year-old, self-described New York Anarchist—who allegedly used Twitter to advise protesters at the Pittsburgh economic summit where police would be stationed so they could evade the officers.

FBI agents obtained a search warrant of Madison’s home Thursday. According to court papers filed by his attorney, the agents confiscated computers and leftist political writings from Madison’s home in Queens, New York.